Don't know if there was such Q&A on Eu, but on RU, about month ago, players asked some questions which WG was to asnwer. One of the questions was: When will we have tier IX and X premium tanks? What about price politics?
wg answer( translated, sorry for bad grammar) – we are not planning to introduce tier IX right now. In past tier IX was sometimes last tier to grind to, back then tier 7 and 8 vehicles were very relevant. But time has passed, game has changed, and premiums have not. And now, tier 7s have went out of fashion, and tier 8s have turned from pre-top tanks, into almost medium tier tanks. And about tier 9s, we announced a tank for Frontline, by this, we are testing relevance and safety of such vehicles. About price politics, we don't know yet.
Премиум техника / Как скоро будет премиум техника IX и X уровней? Какая ценовая политика ожидается?